题干

一个初动能为E的小物块从斜面底端冲上足够长的斜面,返回斜面底端时速度大小为,该过程物体克服摩擦力做功为。若小物块冲上斜面的初动能变为2E,则(   )

A:返回斜面底端时动能为

B:返回斜面底端时动能为

C:返回斜面底端时速度大小为

D:返回斜面底端时速度大小为

上一题 下一题 0.0难度 选择题 更新时间:2011-02-11 01:23:27

答案(点此获取答案解析)

D

同类题2

阅读理解

    A cab company in one of Japan's major cities is introducing silent taxi drivers. Miyako Taxi, which is based in Kyoto, shows the new idea in March. The business is currently operating five “Silence Taxis” across the city.

    The cars look like any ordinary taxi,but a notice written on the back of the passenger seat  inform passengers that they have entered one of the new silent fleet. Drivers will offer a greeting when their passenger enters the car, and aside from confirming the route they will not engage in small talk. The drivers can indulge in conversation, only if they are spoken to first, and they are also allowed to communicate in emergency situations.

    Announcing the idea, Miyako Taxi said: “This service is currently in a trial stage, with the goal of creating an in-car atmosphere that provides the most comfortable ride for passengers through limiting the driver's speaking.” According to Japan Today, they made the move after hearing reports from passengers that they were fed up being forced to chat with their drivers.

    The company will assess the popularity of the trial before deciding whether to expand it and roll it out across more of their drivers.

    Language and speaking is at the heart of another issue facing Uber drivers, after lost a High Court Battle to block written tests in London. Drivers applying for a minicab license in the capital will now have to pass the written exam following Uber's failed challenge against Transport for London (TfL). The company argued it could see up to 33,000 existing drivers lose their licences under the new rule.

    The company's London head, Tom Elvidge: vowed to challenge the rule and said, “We've always supported spoken English skills, but writing an essay has nothing to do with communicating with passengers or getting them safely from A to B.”